The document outlines six essential elements of a fair-play mystery: 1) The detective must be memorable to distinguish them from others. 2) The crime must be significant like murder, blackmail, or theft. 3) The criminal must be a worthy opponent to match the detective's intellect. 4) All suspects, including the criminal, must be introduced early on. 5) All clues discovered by the detective must be available to the reader. 6) The solution must be logical when revealed to tie all the clues together.